Bearing cartridge assembly for a turbocharger

ABSTRACT

A turbocharger assembly including a housing, a shaft, and turbine and compressor wheels mounted on opposite ends of the shaft. The shaft is rotatably supported within the housing by a bearing cartridge that includes turbine-side and compressor side ball-bearing assemblies that are longitudinally spaced by a spacer. There are two times as many rows of ball-bearings included in the turbine-side ball-bearing assembly compared to the compressor-side ball-bearing assembly. The spacer slides over and rotates with the shaft and has at least one flat. An optical sensor extends through the housing and an optical sensor opening in the bearing cartridge to prevent the bearing cartridge from rotating within the housing. The optical sensor detects rotational speed of the spacer by counting the number of times the flat(s) passes by the optical sensor during a pre-determined time interval.

FIELD

The subject disclosure generally relates to turbochargers for internalcombustion engines. More particularly, an improved bearing cartridgeassembly for a turbocharger is described herein.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

A turbocharger is a turbine-driven forced induction device thatincreases the efficiency and power output of an internal combustionengine by forcing extra air into the combustion chamber compared tonaturally aspirated engines. Turbochargers are used in a wide variety ofinternal combustion engines, including gas, diesel, alcohol, andmethanol fueled engines. Turbochargers are used in engines to increaseintake air flow with a resulting horsepower gain/advantage.

Turbochargers typically include a turbine wheel that is arranged incommunication with exhaust flow from the internal combustion engine anda compressor wheel that is arranged in communication with intake airflowing into the internal combustion engine. The turbine wheel andcompressor wheel are both mounted to a shaft that is rotatably supportedwithin a housing by a bearing assembly. The turbine wheel includes aplurality of turbine blades that are positioned in the exhaust flow suchthat the turbine wheel is rotatably driven by the exhaust flow as itflows through the plurality of turbine blades. The compressor wheelrotates at the same speed as the turbine wheel such that the compressorblades increase the speed and pressure of the intake air flowing intothe internal combustion engine for increased power delivery.

In typical turbochargers, the bearing assembly that supports the shaftin the housing includes one bearing on the turbine-side of the shaft andone additional bearing on the compressor-side of the shaft. Each bearingmay include inner and outer races with a plurality of ball bearingspositioned radially between the inner and outer races. In someturbochargers, the bearings are lubricated by grease, while in otherturbochargers the bearings are lubricated by oil in an “open bath”lubrication arrangement. Despite advances in turbocharger and bearingdesigns, bearing failure is still a primary failure mode forturbochargers. Thus, the need for more durable turbocharger bearingassemblies with less drag (i.e., less rotating inertia and rotatingresistance) remains.

SUMMARY

This section provides background information related to the presentdisclosure and is not necessarily prior art.

In accordance with one aspect of the subject disclosure, a turbochargerassembly is provided. The turbocharger assembly includes a housing, ashaft, a turbine wheel, and a compressor wheel. The shaft is rotatablysupported within the housing by a bearing cartridge. The turbine wheeland the compressor wheel are mounted on opposite ends of the shaft andare disposed within the housing. The turbine wheel and the compressorwheel both have a plurality of blades. The housing includes a cartridgereceiving bore that receives the bearing cartridge. The bearingcartridge extends co-axially about and supports the shaft at a locationpositioned longitudinally between the turbine and compressor wheels. Thebearing cartridge has a bearing cartridge wall that is arranged incontact with the cartridge receiving bore and includes a turbine-sideball-bearing assembly and a compressor-side ball-bearing assembly. Thecompressor-side ball-bearing assembly is disposed adjacent to thecompressor wheel and the turbine-side ball-bearing assembly is disposedadjacent to the turbine wheel. In accordance with an aspect of thepresent disclosure, there are two times as many rows of ball-bearingsincluded in the turbine-side ball-bearing assembly compared to thecompressor-side ball-bearing assembly. For example, in accordance withone aspect of the present disclosure, the compressor-side ball-bearingassembly includes a first angular contact ball-bearing, while theturbine-side ball-bearing assembly includes a second angular contactball-bearing and a third angular contact ball-bearing that are disposedin end-to-end abutting contact with one another.

In accordance with another aspect of the present disclosure, theturbocharger assembly further includes a spacer that is positionedlongitudinally between the turbine-side and compressor-side ball-bearingassemblies. The spacer slides over and rotates with the shaft and has anouter spacer surface with at least one flat. An optical sensor openingextends through the bearing cartridge wall and the turbocharger assemblyincludes an optical sensor that extends through the housing and theoptical sensor opening in the bearing cartridge wall to prevent thebearing cartridge from rotating within the housing. The optical sensoris positioned to detect a rotational speed of the spacer by counting thenumber of times the flat(s) on the spacer passes by the optical sensorduring a pre-determined time interval.

The inventor has found that the durability of turbocharger bearingassemblies can be increased and drag (i.e., rotating inertia androtating resistance) can be decreased when the turbine-side ball-bearingassembly is designed and constructed to provide twice the thrustcapacity as the compressor-side ball-bearing assembly. Instead of simplyincreasing the size of the turbine-side ball-bearing assembly, theinventor has found that providing two times as many rows ofball-bearings (e.g., two angular contact ball-bearings that are disposedin end-to-end abutting contact with one another) in the turbine-sideball-bearing assembly compared to the compressor-side ball-bearingassembly (e.g., one angular contact ball-bearing) in the compressor-sideball-bearing assembly provides better support for the thrust loads onthe shaft and optimizes rotational inertia for improved efficiencies(i.e., less rotating inertia and rotating resistance).

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated,as the same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is a perspective view of an exemplary turbocharger;

FIG. 2 is a side cross-sectional view of the exemplary turbochargerillustrated in FIG. 1;

FIG. 3 is a side cross-sectional view of an exemplary bearing cartridgeof the turbocharger illustrated in FIG. 1;

FIG. 4 is an exploded section view of the exemplary bearing cartridgeillustrated in FIG. 3;

FIG. 5 is a side perspective view of the exemplary bearing cartridgeillustrated in FIG. 3;

FIG. 6 is an exploded perspective view of the exemplary bearingcartridge illustrated in FIG. 3; and

FIG. 7 is a perspective end view of the exemplary bearing cartridgeillustrated in FIG. 3.

DETAILED DESCRIPTION

Referring to the Figures, wherein like numerals indicate correspondingparts throughout the several views, a turbocharger assembly 20 with aunique bearing arrangement is illustrated.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “includes,” “including,” and “having,”are inclusive and therefore specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated degreesor at other orientations) and the spatially relative descriptors usedherein interpreted accordingly.

With reference to FIGS. 1 and 2, an exemplary turbocharger assembly 20is illustrated that generally includes a housing 22, a shaft 24, aturbine wheel 26, and a compressor wheel 28. The shaft 24 has an outershaft surface 30, is rotatable with respect to the housing 22, anddefines a longitudinal axis 32. Both the turbine wheel 26 and thecompressor wheel 28 are mounted to the shaft 24. The shaft 24 may be aone-piece shaft 24, or alternatively may be split into multiplesegments, such as a turbine segment and a compressor segment. The shaft24 extends longitudinally between a turbine end 34 that is connected tothe turbine wheel 26 and a compressor end 36 that is connected to thecompressor wheel 28. The housing 22 includes a turbine section 38, acompressor section 40, and a center section 42 that is positionedlongitudinally between the turbine and compressor sections 38, 40 of thehousing 22.

The turbine section 38 of the housing 22 includes an exhaust inlet 44that is radially spaced from the longitudinal axis 32 and an exhaustoutlet 46 that is aligned with the longitudinal axis 32. The exhaustinlet 44 and the exhaust outlet 46 are configured to bolt to portions ofthe exhaust system of the internal combustion engine (not shown).Exhaust gases enter the housing 22 through the exhaust inlet 44 and exitthe housing 22 through the exhaust outlet 46. The turbine wheel 26 isdisposed in the turbine section 38 of the housing 22 and includes aplurality of turbine blades 48. The flow of exhaust gas pushes againstthe turbine blades 48, which drives rotation of the turbine wheel 26.

The compressor section 40 of the housing 22 includes an air inlet 50that is aligned with the longitudinal axis 32 and an air outlet 52 thatis radially spaced from the longitudinal axis 32. The air inlet 50 isconfigured to receive air from the surrounding environment eitherdirectly or through an intake system (not shown). The air outlet 52 isconfigured to be connected to an intake manifold (not shown) of theinternal combustion engine via an inlet conduit (not shown), which mayoptionally include an intercooler (not shown). The compressor wheel 28is disposed in the compressor section 40 of the housing 22 and includesa plurality of compressor blades 54. Rotation of the turbine wheel 26drives rotation of the compressor wheel 28 via the shaft 24. Thecompressor blades 54 pump air through the compressor section 40 of thehousing 22 as the compressor wheel 28 rotates and discharge the airthrough the air outlet 52 at a higher velocity and pressure (i.e.,boost) for delivery to the internal combustion engine.

With additional reference to FIGS. 3-7, the turbocharger assembly 20includes a bearing cartridge 56 that is received within a cartridgereceiving bore 58 in the center section 42 of the housing 22 in a slipfit. The bearing cartridge 56 extends co-axially about and supports theshaft 24 at a location positioned longitudinally between the turbine andcompressor wheels 26, 28. The bearing cartridge 56 is an assembly thatincludes a turbine-side ball-bearing assembly 60, a compressor-sideball-bearing assembly 62, and a spacer 64 positioned longitudinallybetween the turbine-side and compressor-side ball-bearing assemblies 62.The bearing cartridge 56 extends longitudinally between a first bearingcartridge end 66 and a second bearing cartridge end 68. Thecompressor-side ball-bearing assembly 62 is positioned at the firstbearing cartridge end 66 adjacent to the compressor wheel 28 (i.e., ispositioned longitudinally between the compressor wheel 28 and the spacer64) and the turbine-side ball-bearing assembly 60 is positioned at thesecond bearing cartridge end 68 adjacent to the turbine wheel 26 (i.e.,is positioned longitudinally between the turbine wheel 26 and the spacer64). The bearing cartridge 56 also includes a bearing cartridge wall 70that has an outer bearing cartridge surface 72 and an inner bearingcartridge surface 74 that are cylindrical in shape. The outer bearingcartridge surface 72 is disposed in contact with the cartridge receivingbore 58 of the center section 42 of the housing 22 in a slip fit.

The spacer 64 is configured to slide over and rotate with the shaft 24.More specifically, the spacer 64 extends co-axially about the shaft 24and longitudinally between a first spacer end 76 and a second spacer end78. The spacer 64 is positioned radially between the bearing cartridgewall 70 and the shaft 24 and longitudinally between the compressor-sideball-bearing assembly 62 and the turbine-side ball-bearing assembly 60such that the first spacer end 76 abuts the compressor-side ball-bearingassembly 62 and the second spacer end 78 abuts the turbine-sideball-bearing assembly 60. Although other configurations are possible, inthe illustrated example, the spacer 64 has a cylindrical shape, extendsco-axially about the shaft 24, and includes an outer spacer surface 80with at least one flat 82 (the function of which is explained below) andan inner spacer surface 84 that is arranged in contact with the outershaft surface 30. The outer spacer surface 80 is spaced radially inwardof the inner bearing cartridge surface 74 to define a gap 86 between thebearing cartridge wall 70 and the spacer 64. This gap 86 inside thebearing cartridge 56 extends longitudinally between the compressor-sideball-bearing assembly 62 and the turbine-side ball-bearing assembly 60.

There are two times as many rows of ball-bearings included in theturbine-side ball-bearing assembly 60 compared to the compressor-sideball-bearing assembly 62. More specifically, in the illustrated example,the compressor-side ball-bearing assembly 62 includes a first angularcontact ball-bearing 88, while the turbine-side ball-bearing assembly 60includes a second angular contact ball-bearing 90 and a third angularcontact ball-bearing 92. The second and third angular contactball-bearings 90, 92 of the turbine-side ball-bearing assembly 60 aredisposed in end-to-end abutting contact with one another. Theturbine-side ball-bearing assembly 60 and the compressor-sideball-bearing assembly 62 are each arranged in a slip fit inside thebearing cartridge wall 70, which makes for easy servicing and the first,second, and third angular contact ball-bearings 88, 90, 92 of thecompressor-side and turbine-side ball-bearing assemblies 60 areindividually replaceable.

Each of the first, second, and third angular contact ball-bearings 88,90, 92 has an inboard bearing end 94 a, 94 b, 94 c and an outboardbearing end 96 a, 96 b, 96 c and includes an inner race 98 a, 98 b, 98c, an outer race 100 a, 100 b, 100 c, and a bearing carrier 102 a, 102b, 102 c (or cage), which supports one row of balls 104 a, 104 b, 104 cpositioned at circumferentially spaced apart locations between the innerand outer races 98 a, 98 b, 98 c, 100 a, 100 b, 100 c. The bearingcarrier 102 a, 102 b, 102 c extends annularly about the inner race 98 a,98 b, 98 c such that the bearing carrier 102 a, 102 b, 102 c ispositioned radially between the inner race 98 a, 98 b, 98 c and theouter race 100 a, 100 b, 100 c and includes pockets that hold the balls104 a, 104 b, 104 c and maintain the circumferential spacing of theballs 104 a, 104 b, 104 c. The inner race 98 a, 98 b, 98 c, outer race100 a, 100 b, 100 c, and balls 104 a, 104 b, 104 c may be made from avariety of different materials, including without limitation, ceramicmaterials for improved wear resistance and a reduction in rotating massand inertia.

The inner race 98 a, 98 b, 98 c extends co-axially about the shaft 24and longitudinally between the inboard bearing end 94 a, 94 b, 94 c andthe outboard bearing end 96 a, 96 b, 96 c. The inner race 98 a, 98 b, 98c has a first inner race surface 106 a, 106 b, 106 c that is arranged incontact with the outer shaft surface 30 and a second inner race surface108 a, 108 b, 108 c that is arranged in contact with the balls 104 a,104 b, 104 c. More specifically, the second inner race surface 108 a,108 b, 108 c includes a rounded groove 110 a, 110 b, 110 c that supportsthe balls 104 a, 104 b, 104 c. The outer race 100 a, 100 b, 100 cextends annularly about the bearing carrier 102 and longitudinallybetween the inboard bearing end 94 a, 94 b, 94 c and the outboardbearing end 96 a, 96 b, 96 c. The outer race 100 a, 100 b, 100 c has afirst outer race surface 112 a, 112 b, 112 c that is arranged in contactwith the balls 104 a, 104 b, 104 c and a second outer race surface 114a, 114 b, 114 c that is arranged in contact with the inner bearingcartridge surface 74 of the bearing cartridge wall 70. The first outerrace surface 112 a, 112 b, 112 c includes an asymmetrical indentation116 a, 116 b, 116 c that supports the balls 104 a, 104 b, 104 c andprovides a thrust load support angle 118 a, 118 b, 118 c. The firstangular contact ball-bearing 88 is arranged such that the thrust loadsupport angle 118 a of the first angular contact ball-bearing 88 formsan acute angle with the longitudinal axis 32 that opens/faces towardsthe compressor wheel 28 and therefore is configured to support a firstthrust load 120 a (i.e., an axial load) pointing toward the turbinewheel 26. The second and third angular contact ball-bearings 90, 92 arearranged such that the thrust load support angles 118 b, 118 c of thesecond and third angular contact ball-bearings 90, 92 form acute angleswith the longitudinal axis 32 that open/face towards the turbine wheel26 and therefore are configured to support a second thrust load 120 b(i.e., an axial load) pointing toward the compressor wheel 28.

The bearing cartridge 56 includes a first bearing cartridge opening 122disposed at the first bearing cartridge end 66 and a second bearingcartridge opening 124 disposed at the second bearing cartridge end 68.The inner bearing cartridge surface 74 of the bearing cartridge wall 70includes a first shoulder 126 that is positioned inboard of the firstbearing cartridge end 66 and a second shoulder 128 that is positionedinboard of the second bearing cartridge end 68. The first angularcontact ball-bearing 88 is received within the first bearing cartridgeopening 122 in the first bearing cartridge end 66 in a slip fit and isoriented such that the inboard bearing end 94 a of the first angularcontact ball-bearing 88 abuts the first shoulder 126 of the bearingcartridge wall 70 and the first spacer end 76, while the outboardbearing end 96 a of the first angular contact ball-bearing 88 sits flushwith the first bearing cartridge end 66. The second angular contactball-bearing 90 and the third angular contact ball-bearing 92 are bothreceived within the second bearing cartridge opening 124 in the secondbearing cartridge end 68 in a slip fit. The second angular contactball-bearing 90 is oriented such that the inboard bearing end 94 b ofthe second angular contact ball-bearing 90 abuts the second shoulder 128of the bearing cartridge wall 70 and the second spacer end 78. The thirdangular contact ball-bearing 92 is oriented such that the inboardbearing end 94 c of the third angular contact ball-bearing 92 isarranged in end-to-end abutting contact with the outboard bearing end 96b of the second angular contact ball-bearing 90, while the outboardbearing end 96 c of the third angular contact ball-bearing 92 sits flushwith the second bearing cartridge end 68.

As explained above, the bearing cartridge 56 is configured such that theturbine-side ball-bearing assembly 60 has two times as many rows ofball-bearings compared to the compressor-side ball-bearing assembly 62.The inventor has found that this particular ratio and bearingarrangement provides optimal durability while reducing drag (i.e.,reducing the rotating inertia and rotating resistance) because underthis arrangement, the turbine-side ball-bearing assembly 60 providestwice the thrust capacity as the compressor-side ball-bearing assembly62. As a result of this particular construction, the compressor-sideball-bearing assembly 62 is arranged to counterbalance the thrustcapacity of the turbine-side ball-bearing assembly 60 and stabilize theweight of the turbine wheel 26, which is typically much heavier than thecompressor wheel 28. For example, the compressor wheel 28 is typicallycomposed of light-weight metals or alloys, such as aluminum. On theother hand, due to its placement in the exhaust flow path, the turbinewheel 26 is typically composed of high temperature (i.e., heatresistant) metals or alloys, such as steel, which are considerablyheavier (i.e., more dense). By including two times as many rows ofball-bearings in the turbine-side ball-bearing assembly 60 compared tothe compressor-side ball-bearing assembly 62, the bearing cartridge 56is better able to counterbalance the heavier weight of the turbine wheel26 as compared to the compressor wheel 28. This particular arrangementalso gives the turbine-side ball-bearing assembly 60 added width at theinner and outer races 98 b, 98 c, 100 b, 100 c compared to thecompressor-side ball-bearing assembly 62 for improved durability. At thesame time, the outer diameter of the turbine-side ball-bearing assembly60 remains small so as not to increase the distance between thelongitudinal axis 32 and the balls 104 b, 104 c/outer race 100 b, 100 c,which would lead to an unwanted increase in the rotating inertia of theturbine-side ball-bearing assembly 60.

While the bearing cartridge 56 shown in the illustrated example includesthree rows of ball-bearings arranged at a 2:1 ratio between theturbine-side ball-bearing assembly 60 and the compressor-sideball-bearing assembly 62, it should be appreciated that the number ofrows of ball-bearings may be increased. For example, the compressor-sideball-bearing assembly 62 may further include a fourth angular contactball-bearing (not shown) such that the compressor-side ball-bearingassembly 62 includes two rows of ball-bearings in total and theturbine-side ball-bearing assembly 60 may further include a fifthangular contact ball-bearing and a sixth angular contact ball-bearing(not shown) arranged in end-to-end contact with one another such thatthe turbine-side ball-bearing assembly 60 includes four rows ofball-bearings in total.

The ball-bearings in the bearing cartridge 56 are arranged in anopen-bath lubrication configuration, where the bearing cartridge wall 70includes a compressor-side oil inlet channel 130, one or morecompressor-side oil inlet holes 132, a turbine-side oil inlet channel134, one or more turbine-side oil inlet holes 136, and an oil inletgroove 138. The compressor-side oil inlet channel 130 extendscircumferentially along the outer bearing cartridge surface 72 near thefirst bearing cartridge end 66 and the turbine-side oil inlet channel134 extends circumferentially along the outer bearing cartridge surface72 near the second bearing cartridge end 68. The oil inlet groove 138extends longitudinally along the outer bearing cartridge surface 72(i.e., is parallel to the longitudinal axis 32) between thecompressor-side oil inlet channel 130 and the turbine-side oil inletchannel 134 and is therefore arranged in fluid communication with thecompressor-side oil inlet channel 130 and the turbine-side oil inletchannel 134.

The compressor-side oil inlet hole(s) 132 extend radially through thebearing cartridge wall 70 and are positioned adjacent to thecompressor-side ball-bearing assembly 62 such that the compressor-sideball-bearing assembly 62 is arranged in fluid communication with (andcan receive lubricating oil from) the compressor-side oil inlet channel130 and/or the oil inlet groove 138. The turbine-side oil inlet hole(s)136 extend radially through the bearing cartridge wall 70 and arepositioned adjacent to the turbine-side ball-bearing assembly 60 suchthat the turbine-side ball-bearing assembly 60 is arranged in fluidcommunication with (and can receive lubricating oil from) theturbine-side oil inlet channel 134 and/or the oil inlet groove 138.Lubricating oil can flow out of the compressor-side ball-bearingassembly 62 and the turbine-side ball-bearing assembly 60 and into thegap 86 between the spacer 64 and the bearing cartridge wall 70. Thebearing cartridge wall 70 further includes an oil outlet hole 140 thatextends through the bearing cartridge wall 70 to allow lubricating oilin the gap 86 inside the bearing cartridge 56 to flow out into thecartridge receiving bore 58, where it then collects in thecompressor-side oil inlet channel 130, the turbine-side oil inletchannel 134, and the oil inlet groove 138 for recirculation.

Thus, an oil flow path is defined through the bearing cartridge 56 thatextends from the compressor-side oil inlet channel 130, the turbine-sideoil inlet channel 134, and the oil inlet groove 138, through thecompressor-side oil inlet hole(s) 132 and the turbine-side oil inlethole(s) 136, through the compressor-side and turbine-side ball-bearingassemblies 60, 62, into the gap 86 between the spacer 64 and the bearingcartridge wall 70, and out through the oil outlet hole 140. Gravity mayassist the circulation of the lubricating oil along this oil flow path.As such, the oil outlet hole 140 may be positioned below the shaft 24while the oil inlet groove 138 may be positioned above the shaft 24,such that the oil outlet hole 140 is diametrically opposed from the oilinlet groove 138 relative to the longitudinal axis 32 (i.e., they areoriented 180 degrees apart from one another).

As shown in FIG. 2, the turbocharger assembly 20 also has an opticalsensor assembly 142. The optical sensor assembly 142 includes an opticalsensor 144 that is housed inside a sensor sleeve 146. The sensor sleeve146 is generally cylindrical in shape and includes a threaded portion148 and an unthreaded portion 150. The threaded portion 148 of thesensor sleeve 146 threads into a sensor bore 152 in the center section42 of the housing 22. The unthreaded portion 150 of the sensor sleeve146 projects into the cartridge receiving bore 58 of the housing 22 andextends into an optical sensor opening 154 in the bearing cartridge wall70. The unthread portion of the sensor sleeve 146 terminates at an openend 156 that is longitudinally aligned with the flat(s) 82 on the spacer64 such that the optical sensor 144 has an unobstructed line of sight tothe flat(s) 82 on the outer spacer surface 80. The optical sensor 144detects a rotational speed of the spacer 64 (and thus the shaft 24) bycounting the number of times the flat(s) 82 on the outer spacer surface80 pass by the optical sensor opening 154 during a pre-determined timeinterval. The optical sensor 144 is arranged in electronic communicationwith another electronic device (not shown), such as an electroniccontrol unit (ECU), that processes the signal output of the opticalsensor 144 and provides a rotational speed reading for the turbochargerassembly 20. By way of example and without limitation, the rotationalspeed reading may be expressed in revolutions per minute (rpms) and maybe displayed to a vehicle operator/occupant and/or may be utilized as aninput to electronic vehicle or engine control systems.

Advantageously, this arrangement where the optical sensor 144 sleeveextends through the housing 22 and the optical sensor opening 154 in thebearing cartridge wall 70 prevents the bearing cartridge 56 fromrotating within the housing 22. In addition, as shown in FIG. 7, theoptical sensor opening 154 in the bearing cartridge wall 70 and thus theoptical sensor assembly 142 is circumferentially spaced from the oilinlet groove 138 by an angle 158 that is less than or equal to 90degrees. In other words, the optical sensor opening 154 is positioned inan upper half of the bearing cartridge wall 70 and above thelongitudinal axis 32. This positioning of the optical sensor assembly142 minimizes or eliminates the accumulation of lubricating oil in thesensor sleeve 146, which could otherwise obstruct the line of sight ofthe optical sensor 144.

Many modifications and variations of the turbocharger assembly 20described herein are possible in light of the above teachings and may bepracticed otherwise than as specifically described while within thescope of the appended claims. These antecedent recitations should beinterpreted to cover any combination in which the inventive noveltyexercises its utility. The use of the word “said” in the apparatusclaims refers to an antecedent that is a positive recitation meant to beincluded in the coverage of the claims whereas the word “the” precedes aword not meant to be included in the coverage of the claims.

What is claimed is:
 1. A turbocharger assembly, comprising: a housingincluding a cartridge receiving bore; a shaft extending longitudinallybetween a turbine end and a compressor end along a longitudinal axis; aturbine wheel connected to said turbine end of said shaft; a compressorwheel connected to said compressor end of said shaft; a bearingcartridge disposed within said cartridge receiving bore of said housingthat extends co-axially about and supports said shaft at a locationpositioned longitudinally between said turbine and compressor wheels;said bearing cartridge including a bearing cartridge wall that isarranged in contact with said cartridge receiving bore; and said bearingcartridge includes a turbine-side ball-bearing assembly adjacent to saidturbine wheel and a compressor-side ball-bearing assembly adjacent tosaid compressor wheel, said compressor-side ball-bearing assemblyincluding a first angular contact ball-bearing and said turbine-sideball-bearing assembly including a second angular contact ball-bearingand a third angular contact ball-bearing that are disposed in end-to-endabutting contact with one another.
 2. The turbocharger assembly as setforth in claim 1, further comprising: a spacer extending co-axiallyabout said shaft and positioned longitudinally between said turbine-sideball-bearing assembly and said compressor-side ball-bearing assembly. 3.The turbocharger assembly as set forth in claim 2, wherein said spacerincludes an outer spacer surface with at least one flat.
 4. Theturbocharger assembly as set forth in claim 3, further comprising: anoptical sensor assembly extending through an optical sensor opening insaid bearing cartridge wall and said housing to prevent said bearingcartridge from rotating within said housing; and said optical sensorassembly positioned to detect a rotational speed of said spacer bycounting a number of times said at least one flat on said spacer passesby said optical sensor opening during a pre-determined time interval. 5.The turbocharger assembly as set forth in claim 1, wherein said angularcontact ball-bearings each include an inner race, an outer race, abearing carrier that is positioned radially between said inner race andsaid outer race, and a plurality of balls rotatably supported by saidbearing carrier at circumferentially spaced apart positions.
 6. Theturbocharger assembly as set forth in claim 5, wherein said outer raceof said first angular contact ball-bearing includes an asymmetricalindentation that supports said plurality of balls and provides a firstthrust load support angle relative to said longitudinal axis that openstoward said compressor wheel to support a first thrust load pointingtoward said turbine wheel and wherein said outer races of said secondand third angular contact ball-bearings include asymmetricalindentations that support said plurality of balls and provide a secondthrust load support angle relative to said longitudinal axis that openstoward said turbine wheel to support a second thrust load pointingtoward said compressor wheel.
 7. The turbocharger assembly as set forthin claim 1, further comprising: a compressor-side oil inlet channelextending circumferentially along said bearing cartridge wall andpositioned adjacent to said compressor-side ball-bearing assembly; acompressor-side oil inlet hole extending through said bearing cartridgewall such that said compressor-side ball-bearing assembly is arranged influid communication with said cartridge receiving bore via saidcompressor-side oil inlet hole; a turbine-side oil inlet channelextending circumferentially along said bearing cartridge wall andpositioned adjacent to said turbine-side ball-bearing assembly; and aturbine-side oil inlet hole extending through said bearing cartridgewall such that said turbine-side ball-bearing assembly is arranged influid communication with said cartridge receiving bore via saidturbine-side oil inlet hole.
 8. The turbocharger assembly as set forthin claim 7, further comprising: an oil inlet groove in said bearingcartridge wall that extends between and is arranged in fluidcommunication with said turbine-side oil inlet channel and saidcompressor-side oil inlet channel; and an oil outlet channel extendingthrough said bearing cartridge wall at a location that is diametricallyopposed from said oil inlet groove.
 9. The turbocharger assembly as setforth in claim 1, wherein said turbine-side ball-bearing assembly andsaid compressor-side ball-bearing assembly are each arranged in a slipfit inside said bearing cartridge.
 10. The turbocharger assembly as setforth in claim 1, wherein there are two times as many rows ofball-bearings included in said turbine-side ball-bearing assemblycompared to said compressor-side ball-bearing assembly.
 11. Theturbocharger assembly as set forth in claim 1, wherein saidcompressor-side ball-bearing assembly further includes a fourth angularcontact ball-bearing such that said compressor-side ball-bearingassembly includes two rows of ball-bearings in total and saidturbine-side ball-bearing assembly further includes a fifth angularcontact ball-bearing and a sixth angular contact ball-bearing arrangedin end-to-end contact with one another such that said turbine-sideball-bearing assembly includes four rows of ball-bearings in total. 12.A turbocharger assembly, comprising: a housing including a cartridgereceiving bore; a bearing cartridge disposed within said cartridgereceiving bore of said housing and including a bearing cartridge wallthat is in contact with said cartridge receiving bore; said bearingcartridge comprising a turbine-side ball-bearing assembly, acompressor-side ball-bearing assembly, and a spacer positionedlongitudinally between said turbine-side and compressor-sideball-bearing assemblies; said spacer includes an outer spacer surfacewith at least one flat; an optical sensor opening extending through saidbearing cartridge wall; and an optical sensor extending through saidhousing and said optical sensor opening in said bearing cartridge wallto prevent said bearing cartridge from rotating within said housing andthat is positioned to detect a rotational speed of said spacer bycounting a number of times said at least one flat on said spacer passesby said optical sensor opening during a pre-determined time interval.13. The turbocharger assembly as set forth in claim 12, furthercomprising: a shaft extending longitudinally between a turbine end and acompressor end; a turbine wheel connected to said turbine end of saidshaft; a compressor wheel connected to said compressor end of saidshaft; said spacer being configured to slide over and rotate with saidshaft; said compressor-side ball-bearing assembly positioned adjacent tosaid compressor wheel and including a first angular contactball-bearing; and said turbine-side ball-bearing assembly positionedadjacent to said turbine wheel and including a second angular contactball-bearing.
 14. The turbocharger assembly as set forth in claim 13,wherein said turbine-side ball-bearing assembly further includes a thirdangular contact ball-bearing such that said second and third angularcontact ball-bearings are arranged in end-to-end contact with oneanother.
 15. The turbocharger assembly as set forth in claim 13, whereinthere are two times as many rows of ball-bearings included in saidturbine-side ball-bearing assembly compared to said compressor-sideball-bearing assembly.
 16. The turbocharger assembly as set forth inclaim 13, wherein said compressor-side ball-bearing assembly furtherincludes a fourth angular contact ball-bearing such that saidcompressor-side ball-bearing assembly includes two rows of ball-bearingsin total and said turbine-side ball-bearing assembly further includes afifth angular contact ball-bearing and a sixth angular contactball-bearing in end-to-end contact such that said turbine-sideball-bearing assembly includes four rows of ball-bearings in total. 17.The turbocharger assembly as set forth in claim 13, wherein saidturbine-side ball-bearing assembly and said compressor-side ball-bearingassembly are each arranged in a slip fit inside said bearing cartridge.18. A turbocharger assembly, comprising: a housing including a cartridgereceiving bore; a shaft extending longitudinally between a turbine endand a compressor end along a longitudinal axis; a turbine wheelconnected to said turbine end of said shaft; a compressor wheelconnected to said compressor end of said shaft; a bearing cartridgedisposed within said cartridge receiving bore of said housing thatextends co-axially about and supports said shaft at a locationpositioned longitudinally between said turbine and compressor wheels;said bearing cartridge including a bearing cartridge wall that isarranged in contact with said cartridge receiving bore; and said bearingcartridge includes a turbine-side ball-bearing assembly adjacent to saidturbine wheel and a compressor-side ball-bearing assembly adjacent tosaid compressor wheel, wherein there are two times as many rows ofball-bearings included in said turbine-side ball-bearing assemblycompared to said compressor-side ball-bearing assembly.
 19. Theturbocharger assembly as set forth in claim 18, wherein saidcompressor-side ball-bearing assembly includes a first angular contactball-bearing such that said compressor-side ball-bearing assemblyincludes one row of ball-bearings in total and said turbine-sideball-bearing assembly includes a second angular contact ball-bearing anda third angular contact ball-bearing that are disposed in end-to-endabutting contact with one another such that said turbine-sideball-bearing assembly includes two rows of ball-bearings in total. 20.The turbocharger assembly as set forth in claim 18, wherein saidcompressor-side ball-bearing assembly further includes a fourth angularcontact ball-bearing such that said compressor-side ball-bearingassembly includes two rows of ball-bearings in total and saidturbine-side ball-bearing assembly further includes a fifth angularcontact ball-bearing and a sixth angular contact ball-bearing inend-to-end contact such that said turbine-side ball-bearing assemblyincludes four rows of ball-bearings in total.